The continued proliferation of mobile phone and Internet has provided users with more desirable options for application services and mobility. These two phenomena have an effect on to the growth of mobile internet that changed the way of people do their businesses. Since the workforce is becoming increasingly mobile, the need of mobile email as one of the mobile internet applications is predicted to increase in the near future. However, some security issues are impeding the further adoption of the technology especially for government and business such as the insufficient security protection for privacy and the integrity of the e-mail's message exchange between users as well as the as the authenticity of the users that are vulnerable to security threats. These security threats include message alteration, eavesdropping, and impersonation. In this paper, we develop a simple yet secure mobile messaging system called as Cherri, using hybird cryptosystem based on proprietary stream cipher algorithm and RSA public key algorithm combined with administration server for user registration as well as key management. In this scheme, privacy and integrity of the message is achieved through encryption by using sessuin key and public key for protecting the session key. In addition, the user is authenticated by presenting an identity binding with the public key. A prototype is developed to prove the feasibility of the system and statistical test that has been conducted to prove the randomness of the proprietary algorithm. By using this prototype, the results showed that the average encryption time was 544 ms for 625kb file size, which can be considered small enough for practical use and the proprietary algorithm that is based on chaos has passed the test of DIE HARD statistical test suite. Keywords: Cryptography, Mobile Email, Chaos